Cationic conditioning agents for potash flotation

ABSTRACT

An improved froth flotation process for separating sylvite from a pulp containing sylvite using a water-soluble, high molecular weight, diallyl dialkyl quaternary ammonium polymer as a slime conditioning agent is disclosed.

I United States Patent 1191 1111 3, 82,546 Kirwin et a1. 1451 Jan. 1,1974 CATIONIC CONDITIONING AGENTS FOR 3,165,465 11/1965 Ray; 209/5 xPOTASH FLOTATION 3,259,237 7/1966 Schoeld .1 209/166 X 3,321,649 5/1967De Benedictis. 209/166 X [75] Inventors: Roscoe Conklin Kirwin, Mi land,3,408,292 10/1968 Dajani 210 54 x Tex.; William Lewis Hart, 3,452,8677/1969 Bishop 209/166 Pittsburgh; Joseph Michael Antonetti,Burgettstown, both of Pa. Prima Examiner-Robert Halper [73] AsslgneezCalgon Corporatlon, P1ttsburgh, Pa. Atwmg) Martin L Katz et aL [22]Filed: Dec. 3, 1971 1 [21] Appl. No.: 204,647.

[57] ABSTRACT [52] US. Cl. 209/166, 209/5 [51] Int. Cl B03d 1/02 Animproved froth flotation process for separating syl- [58] Field ofSearch 209/166, 5; 210/53, vite from a pulp containing sylvite using awater- 210/54 soluble, high molecular weight, diallyl dialkyl quaternaryammonium polymer as a slime conditioning agent [56] References Cited isdisclosed.

UNITED STATES PATENTS 2,923,408 2/1960 Williams 209/166 1 3 Claims, 1Drawing Figure FL 014/ D/AGRAM CATIONIC CONDITIONING AGENTS FOR POTASHFLOTATION BACKGROUND OF THE INVENTION This invention is directed to theuse of high molecular weight, water-soluble, diallyl dialkyl quaternaryammonium polymers as slime modifying agents to improve the concentratepurity and yield of sylvite in the potash froth flotation process.

Potash froth flotation is the most commonly employed process forseparating potash values from pulps containing potash. Potash ores minedin the United States and Canada generally'contain from about 5 to 50percent sylvite (KCl) with the balance being primarily halite (NaCl) andthe remainder gangue materials. Generally, the gangue minials found withsylvite/halite ore are clays such as montmorillonite and gypsum alongwith minor amounts ofiron, manganese oxides and other minerals. Theseores are the primary source of potash chemicals for agriculture andindustry.

In order to concentrate and recover the sylvite from the otherconstituents of the ore, a froth flotation process is utilized.Essentially, the potash flotation process comprises the followinggeneral steps. First, the sylvitecontaining ore is crushed and ground ina saturated brine until the ore particles are from 8 to mesh in size.Saturated, brine solution is used throughout the potash flotationprocess since sylvite is soluble in water and any unsaturated water usedin the process would dissolve the ore and result in a loss. The ore pulpis then diluted with additional brine until a consistence of about 20 to40 percent byweight ore solids is obtained. After dilution, the variousconditioning agents, collecting agents, and frothing agents are added tothe ore slurry. The pulp is then aerated to produce a froth at the pulpsurface. The potash values are concentrated in the froth and theremainder of the ore consisting essentially of halite and gangue remainsin the aqueous pulp phase. The potash-bearing froth is then separatedfrom the residual pulp and further processed to obtain the desiredmetal. The residual liquid pulp generally referred to as the flotationtailings is then further sub jected to additional frothing steps if itcontains a sufficiently high concentration of potash. If not, thetailings are discarded. lt is safe to say that the majority of potashflotation processes follow the above sequence. However, it should benoted that many additional but optional steps such as scrubbing,desliming and classifying are commonly employed and many variations ofthe above-described general process have found wide acceptance in theart.

agents for potash flotation are the fatty amines, especially the aminesalts such as octylamine hydrochloride and octadecylamine acetate.

Frothing agents are compounds which dissolve in the pulp solution andhave both a polar and nonpolar group in the molecule. These compoundschange the air-pulp solution interface tension thereby helping toproduce a voluminous body of bubbles at or above the surface of theflotation pulp and also helping to prolong the life of the bubbles soproduced. The most commonly employed frothing agents for the potashflotation process are the C to C aliphatic alcohols.

In addition to the collecting agent and frothing agent, a conditioningagent is usually employed. Both the col lecting agent and frothing agenthave a tendency to be consumed by the gangue, especially clay.Therefore, as much of the gangue is removed by mechanical means that ispracticable. Thereafter, it is necessary to add a conditioning agentwhich decreases the attraction of the gangue for the collecting andfrothing agents. This type of conditioning agent is commonly called aslime blinder or slime depressant. The most commonly used deslimers usedin potash flotation processes are starch and other carbohydratepolymers. For example, see

Fast et a], US. Pat. No. 3,456,790. Recently, high molecular weightpolymers have. been utilized as slime blinders. For example, see Bishop,U. S. Pat. No.

In the potash flotation process, it is desirable to re- I cover as muchof the potash value from the ore as possible, yet doing so in aselective manner. That is, it is the object of the flotation process torecover as much of the potash from the ore as possible without carryingover the halite and gangue with the potash or without leaving highconcentrations of the potash compounds in the gangue tailing s. In orderto accomplish this selectivity, many collecting, frothing, andconditioning agents have been employed.

A collecting agent for the potash flotation process is one whichpreferentially adheres to the sylvite but not to the halite therebyproducing a water repellent coating on the potash particles. The airbubbles will then cling to the potash particles and concentrate them inthe froth. The most commonly employed collecting SUMMARY OF THEINVENTION The present invention is directed to a conditioning agent,particularly to a conditioning agent which increases the potash yield byacting on the gangue (slime). More particularly,'the present inventionis directed to the use of high molecular weight, watersoluble, diallyldialkyl quaternary ammonium polymers as conditioning agents forincreasing the potash recovery in potash flotation processes.

We have found that high molecular weight, watersoluble, diallyl dialkylquaternary ammonium polymers increase the efficiency of the potash frothflotation process. The polymers of our invention increase the rate ofpotash recovery and also yield a higher grade concentrate. While we donot wish to be bound by any theories, it appears that the polymersincrease the rate of recovery and the concentrate grade by selectivecoagulation of the slime. It is undisputed that the presence of slimesis detrimental to most flotation processes. The slimes adsorb largequantities of collecting agents and frothing agents thereby hinderingthe flotation process. In addition, the slimes entrap the potashparticles and are, therefore, a large source of lost mineral values.Finally, the slimes themselves may be carried over in the froth if theyhave adsorbed the collecting agents. However, by selectively coagulatingthe slime and reducing the total surface of the slime, the processefficiency is increased. First of all, less amount of collecting agentsand frothing agents are adsorbed by the slime. This leads to an increasein efficiency since more of the agents are available for the potashparticles and less of the slime is found in the froth. In addition, thecoagulated slime does not entrap the potash particles and the coagulatedslime is less likely to he found in the froth. Therefore, is appearsthat the polymers of our invention increase the flotation process byselectively blinding the slime.

CH-Cl-l where R is hydrogen or an alkyl group of l to 18 carbon atoms.The preparation and use'of this class of compounds is illustrated inButler U.S. Pat. No. 3,288,770, Boothe U.S. Pat. Nos. 3,461,163 and3,472,740, Schuller et a1 U.S. Pat. No. 2,923,701 and Booth et a1. U.S.Pat. No. 3,147,218. The preferred diallyl dialkyl polymers are when R isa lower alkyl group of l to 4 carbon atoms, preferably methly.

The polymers of our invention may be prepared by polymerizing thecationic monomer using any of the well known solution, emulsion orsuspension techniques. We have prepared effective polymers using allthree of these methods. Our invention is independent of the method ofpreparation so long as the resulting polymer is a water-soluble, highmolecular weight cationic polymer of diallyl dialkyl quaternary ammoniumchlorides. I

As mentioned above, the polymers of our invention are prepared bypolymerizing the quaternary ammonium monomers. lt is also within thescope of our invention to use copolymers of two or more differentquaternary ammonium compounds. It is also within the scope of ourinvention to use polymers containing groups derived from monomers inaddition to the cationic monomers. Our invention contemplates the use ofcopolymers containing up to about 97.5 mole percent of otherwater-soluble comonomers and up to about l mole percent ofwater-insoluble comonomers. Examples of some of the useful water-solublecomonomers are acrylamide, methacrylamide, diacetone acrylamide and theN-lower alkyl substituted acrylamides and methacrylamides. Examples ofsome of the waterinsoluble comonomers are vinyl acetate, acrylonitrile,vinyl chloride, styrene, and the lower alkyl esters of acrylic andmethacrylic acid. Therefore, while the polymers of our invention consistessentially of diallyl dialkyl quaternary ammonium compounds, they mayalso contain up to about 97.5 mole percent of other watersolublemonomers and up to about mole percent of water-insoluble comonomers andstill be within the scope of our invention. The diallyl dialkylquaternary ammonium polymers of our invention are watersoluble, highmolecular weight and contain at least 2.5 percent diallyl dialkylquaternary ammonium compounds. The preferred polymers of our inventioncontain at least 5 percent diallyl dialkyl quaternary ammonium compoundsand the preferred comonomer is acrylamide.

The molecular weight of the polymers may be as low as 1,000 or as highas 10,000,000 or higher. We have found that generally the highermolecular weight polymers are somewhat better than low molecular weightpolymers. There is no reason to believe that there is a critical minimummolecular weight which must be achieved in order to show an improvedflotation process. However, for all practical purposes, a minimummolecular weight of about 10,000 is necessary for economic results.

Similarly, there is no critical minimum concentration that is necessary.A small amount will show a slight effect when compared to a largeramount. However, for all practical purposes, we have found thatconcentrations less than 0.001 pounds per ton based on the weight of thedry ore, will seldom be used. Likewise, concentrations greater than 1.0pounds per ton will seldom be used. The preferred concentration rangewill differ depending on which ore is being processed. However, in themajority of cases, the concentration of cationic polymer will be fromabout 0.001 to about 0.01 pounds per ton.

The polymers of our invention are added to the flotation process justprior to the flotation step. They are added at the conditioning stagesimmediately prior to flotation. In a typical potash flotation plant,there are several flotation steps. The polymers of our invention may beadded at the conditioning stages prior to any of these flotation steps.FIG. 1 is a flow diagram of a typical potash flotation process. Withreference to FIG. 1, it can be seen that the process has three differentflotation steps where the potash is separated from the undesirableby-products. In FIG. 1, these steps are labeled rougher flotation,cleaner flotation, and recleaner flotation. The polymers of ourinvention may be added prior to any of these flotation steps in order toincrease the efficiency of that particular flotation step. We have foundthat the use of the polymer in the rougher flotation is most beneficialand essential. However, the use of the polymers in the other flotationsteps is optional and will depend on the grade of ore being refined andthe efficiency of the rougher flotation step in removing the slime.

Since the cationic polymers of our invention work on the gangue, theyare effective in processing other solu-' ble salts which may be refinedby froth flotation. For example, they may be used in the flotation ofhalite from sylvite, langbeinite from halite, sodium bicarbonate fromhalite and many others.

We have performed numerous experiments which demonstrate theeffectiveness of our invention. The following experiments illustrate ourinvention but should not be considered to limit the same.

A series of experiments were performed in the laboratory to demonstratethe effectiveness of cationic polymers in the recovery of potash valuesvia froth flotation. The experiments were performed in a modifiedfive-liter laboratory Denver flotation cell in the laboratory ofSouthwest Potash Companys Carlsbad, N.M. plant. The ore sample was takendirectly from the plant processing stream. The following procedure wasfollowed in running the experiments. A bucket of the ore from the plantwas run through a proportioner three times. The proportioner divided thesample in halves each time through with one half being recycled and theother half discarded. The sample from the proportioner weighed about2,000 grams and was approximately one eighth of the original bucket.Saturated brine was then added to the 2,000 grams of ore so that thetotal weight was about 3,380 gramsl This ore slurry was stirred forabout 20 minutes and subjected to three desliming operations. The firstdesliming step had a settling time of l and a half minutes, the secondhad a settling time of 1 minute and the final desliming step had asettling time of a half minute. After the desliming steps, a slimeblinder was added to the ore pulp and mixed for about 2 minutes. Thenthe collecting and frothing agents were added and the pulp mixedvigorously for an additional minute. The pulp was then added to theflotation cell and the level of the cell adjusted to just below the lipwith saturated brine. The cell was turned on and the pulp was floatedfor 3 minutes or slightly longer (until done). The concentrate and tailswere then collected, filtered, dried, cooled and weighed. They were thenpulverized and analyzed spectrometrically for K 0.

Table 1 gives the results of the laboratory tests performed on the oresamples taken during a one day period. The ore was -8 mesh. The slimeblinders tested were guar gum (Guar), a high molecular weight, slightlyhydrolyzed polyacrylamide (PAM) and a higher molecular weighthomopolymer of dimethyl diallyl ammonium chloride (DMDAAC). The otheragents employed for collecting and frothing were an amine collector,methoxy propylene glycol and methyl isobutyl carbinol.

TABLE 1 Blinder Percent Percent Percent Percent in lbs. K 0 in K 0 in KO in K,O [Ton Feed Concentration Tails Recovered Guar 0.08 17.37 56.771.18 95.10 0.08 17.78 57.48 1.90 92.13 0.08 17.89 56.37 1.50 90.80 PAM0.02 17.50 56.52 0.85 96.38 0.03 17.51 55.64 0.35 96.55 0.04 17.27 56.310.82 96.57 DMDAAC Table 1 clearly illustrates the effectiveness ofdiallyl dialkyl quaternary ammonium polymers, especially DMDAAC, asslime blinders in the potash flotation process. The cationic polymer wasmore effective at lower concentrations than guar gum or polyacrylamide.

Table 11 gives the results of the laboratory tests per formed on aseries of ore samples taken during a one day period. The ore was -6 meshand the agents employed are the same as mentioned for Table 1 above.

TABLE 11 Blinder Percent Percent Percent Percent in lbs. K 0 in K,O inK,O in K 0 lTon Feed Concentration Tails Recovered Guar 0.08 17.30 56.381.88 91.96 PAM 0.03 17.56 55.91 1.62 93.77 DMDAAC Table 11 alsoillustrates that the cationic polymers are more effective at lowerconcentrations that the heretofore employed slime blinders. 1n the abovetables, the additional mineral recovery caused by the use of thecationic polymer is in the neighborhood of about 1 percent. However,this small improvement is of great economic importance since manycommercial operations process 50,000 tons or more of ore daily. Withthis very high throughput rate, relatively small improvements in thepercent potash recovery yields many additional tons of product. Inaddition, the lower dosages of additives needed give a considerablesavings when one considers the high throughput rate.

Table 111 gives the results of laboratory tests performed on a series ofthree ore samples. The ore was -8 mesh and the agents employed are thesame as for Table 1 above. In these tests, the guar and polyacrylamidewere used together.

TABLE 111 Percent" Percent Percent Blinder in in ,0 in 2 Pounds/TonConcentration Tails Recovered Guar PAM .06 .02 57.72 1.57 94.87 DMDAACTable IV gives the results of laboratory tests which were performed thesame as for Table 111.

TABLE IV Percent Percent Percent Blinder in K 0 in ,0 in K,O Pounds/TonConcentration Tails Recovered Guar PAM .06 .02 56.12 1.45 95.09 DMDAACThe results in Tables 111 and 1V illustrate that the cationic polymersof our invention are more effective at lower dosages than a combinationof both guar and polyacrylamide.

We have performed many additional experiments using various othercationic polymers. The results of these experiments clearly indicatethat high molecular weight, diallyl dialkyl quaternary ammonium polymersare effective slime blinders in the potash flotation process.

We claim:

1. An improved potash froth flotation process comprising grinding thepotash ore, mixing the ground ore with water to form an ore pulp,aerating the pulp to form a froth and collecting and processing thefroth wherein the improvement comprises adding to the ore pulp duringsaid flotation process, but prior to frothing, a water-soluble, highmolecular weight, diallyl dialkyl quaternary ammonium polymer consistingessentially of dimethyl diallyl ammonium chloride as a conditioningagent.

2. An improved potash froth flotation process comprising grinding thepotash ore, mixing the ground ore with water to form an ore pulp,aerating the pulp to form a froth and collecting and processing thefroth wherein the improvement comprises adding to the ore pulp duringsaid flotation process, but prior to frothing, from about 0.001 to about0.01 pounds per ton based on the weight of the dryore 'of awater-soluble, high molecular weight,polymer consisting essentially ofdimethyl diallyl ammonium chloride as a conditioning agent, said polymerhaving a molecular weight of at least about 10,000.

3. An improved process as in claim 2 wherein the potash ore is sylvite.

2. An improved potash froth flotation process comprising grinding the potash ore, mixing the ground ore with water to form an ore pulp, aerating the pulp to form a froth and collecting and processing the froth wherein the improvement comprises adding to the ore pulp during said flotation process, but prior to frothing, from about 0.001 to about 0.01 pounds per ton based on the weight of the dry ore of a water-soluble, high molecular weight, polymer consisting essentially of dimethyl diallyl ammonium chloride as a conditioning agent, said polymer having a molecular weight of at least about 10,000.
 3. An improved process as in claim 2 wherein the potash ore is sylvite. 